1. Field of the Invention
The present invention relates to an improved valve driving apparatus that employs a drive source, such as a motor, to drive a valve that is formed of a spherical member that opens or closes a flow path.
2. Related Art
As conventional apparatuses for opening or for closing refrigerant flow paths, which are used for refrigerators or for air conditioners to adjust the temperatures in chambers that communicate with the flow paths, presently available valve driving apparatuses employ solenoid valves (see JP-A-62-288780) or needle valves as opening and closing valves.
However, the valve opening and closing operations performed by a valve driving apparatus for which a solenoid is employed are very noisy. And since regardless of whether a solenoid is open or closed, to maintain an existing state the solenoid must remain conductive at all times, another problem with a solenoid apparatus is related to the power it consumes. As another drawback, a valve driving apparatus that uses a solenoid is so designed that both valves can not simultaneously be held open, or closed.
The valve driving apparatus that employs the needle valves uses a stepping motor, for example, as a drive source, and converts the rotational force of the stepping motor into a thrusting force for a needle valve to open and close a flow path. Of course, when compared with a valve driving apparatus that uses a solenoid, a valve driving apparatus that uses needle valves produces less noise when operating.
Since the valve driving apparatus that uses needle valves must normally convert the rotational force produced by the stepping motor into a thrusting force for a needle valve, screw threads that engage each other are provided along the outer surface of the rotary shaft of the motor and the inner surface of a cylindrical member positioned around the rotary shaft. As the rotary shaft of the motor is rotated while engaging the cylindrical member, the rotor of the motor moves linearly along the cylindrical member, and as a result, the needle valve, which is attached to the distal end of the output shaft of the motor, moves linearly with the output shaft. This linear movement of the needle valve opens or closes an aperture.
However, for the valve driving apparatus using the needle valve, generally, one motor corresponds to one needle valve, so that a plurality of valves can not be operated by a single motor. That is, a valve driving apparatus that uses needle valves is not appropriate for a three-way valve or a four-way valve that has a plurality of flow paths (Apertures). In addition, for a valve driving apparatus that employs needle valves, it is technically difficult to form the screw threads for the cylindrical member and the output shaft. In other words, in order to smoothly rotate the output shaft of the motor while engaging the cylindrical member, the screw threads in the cylindrical member and the screw threads in the output shaft must be machined very precisely. Further, a precise process is required to align the center position of a needle valve, which is attached to the distal end of the rotary shaft of the motor, and the center position of a flow path (an aperture) into which the needle valve is to be. inserted. Therefore, a high-degree of technical skill and experience are required for the assembly of such a valve driving apparatus.
It is, therefore, one objective of the present invention to provide a valve driving apparatus that can be applied for a three-way valve and a four-way valve, while complex skills and experience, such as are required for precise screw thread machining and the aligning of the center positions of a valve and an aperture, are not required.
An aspect of the present invention, there is provided a valve driving apparatus includes a main body coupled with an inflow tube for introducing a fluid internally and a discharge tube for discharging said fluid, valve members movable within a predetermined range, said valve members permitting the opening or the closing of apertures connected to one of said inflow tube and said discharge tube which is coupled with said main body, a driver for driving said valve members, said driver including cam members having cam faces used for operating said valve members and a drive source for driving said cam members, wherein said valve members are operated by rotating said cam members to open and close said apertures.
According to the present invention, the valve driving apparatus of the invention includes a cam member that has a cam face as a driver, and valve members are moved by the cam face of the cam member so as to open or close apertures in the main body. Thus, the screw threads that are used for a conventional valve driver are not required, and as a result, complicated operations, such as the precise machining of screw threads and the aligning of the center positions of valve members and apertures, are not required, and a simple structure can be provided whereby: the apertures can be opened and closed by the valve members. Therefore, not only the number of required parts but also manufacturing expenditures, such as assembly costs, can be reduced, and mass production can be used to produce inexpensive valve driving apparatuses.